Previously, calcium carbonate has been incorporated at a high concentration in the utility of a plastisol in which a vinyl chloride resin or an acrylic resin and a plasticizer are mixed, and the sealant field in which a urethane resin or a silicone resin, a polysulfide resin etc. are mixed. On the other hand, among synthetic resins, for example, in the field having a high processing temperature such as a polyester resin, a representative of which is polyethylene terephthalate (PET), an engineering plastic, a representative of which is polyamide (PA), polycarbonate (PC), or polyphenylene sulfide (PPS), calcium carbonate has previously been incorporated at a very small amount for the purpose of a light diffusing material, an anti-blocking material etc.
For example, a porous white PET film, produced by a method of forming porous voids at an interface between a PET resin and a micropore forming agent by a method of adding calcium carbonate whose particle size has been adjusted as a micropore forming material together with a non-compatible resin to a PET resin, and stretching this into a film (sheet) (Patent Reference 1), or a method of adding an inorganic fine particle such as barium sulfate etc. to a PET resin, and stretching this into a film (sheet) (Patent Reference 2) has been practicalized in a wide variety of fields such as a synthetic paper, a (prepaid) card, a label, an optical reflecting film (sheet) etc. Among them, for example, in the case of a light reflecting film utilized in the utility of liquid crystal TV, high image quality, wide screen, and low cost of liquid crystal TV are required.